Hello,
Are you hoping to do surround with the four speakers?
or double up two left and two right speakers? Do you have a fifth speaker for center channel (voices, dialogue )?
the HDMI ARC will have surround sound imbedded. An inexpensive Marantz AVR does 5 channel audio processing and has 5 or 7 speaker outputs, HDMI input and streams and Bluetooth. The cheaper Marantz are less deep but still 15”.
As said above, you can double two speakers on one output if the amp can handle the load.
Personally I would just consider wiring the four speakers in double stereo. For this you don’t have to use HDMI, as the toslink from the tv will also work fine. You can run the tv audio as well for the dialogue and fill in with the ceiling speakers. There may be more streaming amps available if you drop the HDMI prerequisite.